This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Using human kidney samples, genotypes and expression levels have been obtained for transporters and selected transcription factors. Association studies will be conducted to find genetic determinants of expression level variation in humans for important drug transporters.